This invention relates to a weighing pan for weighing-out articles to be packaged batchwise, especially but not exclusively for use in combination weighing of irregularly shaped articles, and comprising a pair of opposed sidewalls and at least one pivotable closure flap for controlling an article discharge opening defined between the sidewalls.
Combination weighing has proved to be well-suited for the metering of ready-for-sale batches or portions of many different commodities, including potatoes and other vegetables, when it is desired that the weight of the individual batches or portions shall deviate as little as possible from a prescribed nominal weight. In the interest of the consumers the nominal weight is often a minimum weight. Especially in the case of articles, such as potatoes, which exhibit a relatively large scatter in the weight of the individual articles, the attainable accuracy, which in practice can be expressed as the percentual difference between the average value of a suitable number of successively weighed-out portions (e.g. 20 to 30 portions) and said nominal weight, increases rather fast with the number of weighing pans in the weighing machine employed because with more weighing pans there are more combinations of subportions of correspondingly different weights to choose from.
Computer-controlled combination weighing has been known in the art for several years and detailed description of various embodiments of the method can be found, inter alia, in several patent specifications. In the present context it should be sufficient to recall that according to the general principle of the method each portion is composed of two or more subportions chosen from a larger number of subportions, each of which has been weighed-out in one weighing pan of the machine. From each weighing pan the computer receives an input signal indicative of the weight of the article or articles forming the subportion present in that pan. The computer calculates all possible combinations of the input signals received and chooses that combination which exhibits the smallest difference (with or without regard to the sign of the difference, as the case may be) from the desired or nominal weight of the complete portion. Finally the computer transmits output signals ordering the selected weighing pans, i.e. those belonging to the combination chosen, to open their closure flaps. The subportions thus discharged are collected and packed in any appropriate manner, and as soon as the closure flaps have been reclosed a new weighing cycle can be initiated by supplying articles to the now empty pans. The subportions present in the remaining, non-selected pans are retained therein and the input signals from these pans have been stored in the computer ready for use in the computation etc. of the next weighing cycle.
The number of weighing pans, which can be incorporated in a weighing machine, will however be limited, partly from pure considerations of space and partly by the need for keeping the paths through which the individual subportions are transferred from a weighing pan to a package, reasonably short. The last motive is especially prominent when the weighing pans are arranged in a line side by side, which in itself results in the advantage, compared with an arrangement of the weighing pans in a circle around a central discharge aperture, that when the closure flaps of all selected weighing pans are opened simultaneously, the individual articles or subportions do not arrive simultaneously at the discharge aperture of the weighing machine which consequently is less subject to the risk of being blocked.